Selective catalytic reduction (SCR) systems have been used to reduce automotive emissions. However, degraded performance in SCR systems may be related to a plurality of sources. For example, the injection system, the SCR catalyst, and the reductant quality as well as various other potential sources may be root cause for degraded performance.
One way to identify a potential source of degraded performance may be to determine degraded performance of the emission control system whereby an inspection of the system may be performed for diagnosis. However, under some conditions, such as during travel in remote areas, a mechanical diagnose of the system may be inconvenient. Further, it may be desirable to isolate a source of potential degraded performance within the emission control system so as to operate the vehicle such that various other strategies may still be used to control emissions.
In one approach, a method may be used that identifies which of a plurality of potential degradation sources is at least partially responsible for causing degraded output of a urea-based NOx reduction system by considering and correlating each of the plurality of sources. In another approach, a method of operating an internal combustion engine having an emission control system is provided. The method comprises, during degraded performance of the emission control system, dynamically identifying a relationship between a plurality of operating conditions of the emission control system, and correlating the relationship to one or more sources of degraded performance of the emission control system. Additionally, or alternatively, the method may distinguish one or more sources of degraded performance from a plurality of potential sources of said degraded performance based on said relationship. In this way, accurate identification of a source of degradation among a plurality of potential sources is possible, even when each of the potential sources may be responsible for the degradation.
In still another approach, a method of diagnosing an emission control system may be used that comprises: during degraded performance of the emission control system, dynamically identifying a relationship between a plurality of operating conditions of the emission control system, and correlating the relationship to a plurality of potential sources of degraded performance of the emission control system to identify at least one degraded source among said plurality of potential sources.